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NO
YES
Is the
Thermostat
Calling
for Heat?
Is There
24 VAC
on the Gas
Valve?
NO
Is the
Indirect
Calling
for Heat?
NO
NO
YES
Is the
Red LED
(LOW WATER)
On?
The Control is
Sensing
Low Water.
Is the
Yellow LED
(HI TEMP)
On?
The Control is
Sensing High
Temperature.
If both the red and yellow LEDs are off and
there is a call to fire the burner, there will be 24
VAC on the gas valve.
If 24 VAC is not present, the control should
be replaced.
The control is supplying 24 VAC to the burner circuit.
Recheck wiring to the gas valve terminals.
Check for manifold and supply gas pressure.
Replace gas valve if no main flame.
The Control
is Operating
Properly.
Replace
Control
The burner will not fire until the boiler water has dropped to the
high limit differential set-point (10° below high limit setting).
Check that the high temperature setting is correct.
Zone or boiler pump could be malfunctioning or system could be air
bound if boiler remains off without heat going to emitters.
Troubleshooting Flow Chart 1 – Burner Will Not Fire
YES
YES
NO
Is the
Yellow LED
(TARGET)
On?
The Boiler has
Reached the
Target
Temperature.
When the ECONOMY function is active, the control monitors heating
demand and establishes Target boiler temperatures below the high
limit setting to conserve fuel. The burner will not fire until the boiler
temperature drops to the automatically calculated Target Temp Differential.
YES
NO
Is the
Green LED
(TEMP ACTIVE)
On?
The Control is
Not Powered.
The Temp Active LED will be on at all times when the control is
powered.
Check for 120 VAC on the control input.
YES
NO
The burner
will not fire unless there is
a call from the thermostat
or an external zone.
Set thermostat to call for
heat. Burner should fire.
YES
CAUTION – ALWAYS ALLOW A BOILER TO COOL BEFORE ADDING WATER
The burner will not fire until the low water condition is satisfied.
Check that the system is filled with water.
Check that the sensor is inserted fully into the well and contact
between its spring clip and the copper well tube is made.
Also see
for additional troubleshooting information.
Ensure boiler pump is running and there is flow. If the boiler is
hot and not cooling down there is likely a flow issue.
11.C.1 Troubleshooting Flow Chart 1 (burners off)
Section 8.C.3
M
INI-
T
HERM
JX
Residential Boilers
®
